Method of detecting accessories on an audio jack

ABSTRACT

An apparatus comprises an audio or video jack connector configured to receive an audio or video jack plug of a separate device, a detection circuit in electrical communication with the connector, and a processor communicatively coupled to the detection circuit. The connector includes an electrical contact for connection to a conducting terminal of the plug. The detection circuit is configured to determine a resistance at the conducting terminal. The resistance is a resistive load of the separate device at the conducting terminal of the plug. The processor is configured to identify a function of the separate device according to the determined resistance, and configure an operation of the apparatus according to the determined function.

BACKGROUND

Many types of electronic devices are available for providing managementof personal information and for providing personal media entertainment.Some of these devices play audio media and video media such as slideshows, music, movies, and other video programs. Examples, include apersonal computer, a personal data assistant, an MP3 player, and a cellphone. Users may want different device capabilities based on the type ofmedia involved and may want to mix and match accessories with the mediaplayers. To provide the accessories the users may need a basic level ofsophistication to determine device compatibility and to get differentdevices to interact.

OVERVIEW

This document relates generally to systems and methods for automaticallydetecting a device when it is connected to a host device, and inparticular, to detecting the presence and type of an accessory devicefrom the interconnection with the host device.

An apparatus example includes an audio or video jack connectorconfigured to receive an audio or video jack plug of a separate device,a detection circuit in electrical communication with the connector, anda processor communicatively coupled to the detection circuit. Theconnector includes an electrical contact for connection to a conductingterminal of the plug. The detection circuit is configured to determine aresistance at the conducting terminal. The resistance is a resistiveload of the separate device at the conducting terminal of the plug. Theprocessor is configured to identify a function of the separate deviceaccording to the determined resistance, and configure an operation ofthe apparatus according to the determined function.

A method example includes detecting that an audio or video jack plug ofa first device is inserted into an audio or video jack connector of asecond device, determining a resistance at least one conducting terminalof the plug using the second device, identifying, using the seconddevice, a function performable by the first device according to theresistance at the at least one conducting terminal, and configuring thesecond device according to the identified function performable by thefirst device.

This section is intended to provide an overview of subject matter of thepresent patent application. It is not intended to provide an exclusiveor exhaustive explanation of the invention. The detailed description isincluded to provide further information about the present patentapplication.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 is an illustration of an example of an audio and/or video jackplug.

FIG. 2 shows a block diagram of portions of an example of a device toautomatically detect the presence and type of an accessory device towhich it is connected.

FIG. 3 is a block diagram of portions of an example of a detectioncircuit.

FIG. 4 is a flow diagram of an example of a method for automaticallydetecting the presence of an accessory device when it is connected to ahost device.

FIG. 5 is a flow diagram of another example of a method forautomatically detecting the presence of an accessory device when it isconnected to a host device.

FIG. 6 is a flow diagram of an example of a method for automaticallydetecting the presence of an accessory device when it is connected to ahost device and for identifying requested host device operations.

DETAILED DESCRIPTION

This document relates generally to systems and methods for automaticallydetecting the presence and type of an accessory device when it isconnected to a host device. One type of interconnection between anaccessory device and a host device is an audio jack connector or a videojack connector.

FIG. 1 is an illustration of an example of a jack plug of an audio jackor a video jack connector. An audio or video jack connector is sometimescalled a TRS connector. The letters “TRS” stand for tip, ring and sleeveconducting terminals. In some examples, an audio or video jack connectormay be a TS connector having only the tip and sleeve conductingterminals. In the example shown in FIG. 1, the audio or video jackconnector has four conducting terminals and can be called a TRRSconnector for the tip, ring, ring, and sleeve connections.

A jack plug can be included as part of several types of devices, such asa headset, a microphone, and an audio visual (A/V) cable. These devicesare typically accessory devices plugged into a host device such as amedia player or computing device. A user would have to program orotherwise configure the host device uniquely for each type of accessorydevice that was plugged into the host device. It would be convenient forthe user if the host device was able to automatically recognize the typeof device plugged into the audio jack or a video jack connector.

Table 1 shows an example of a signal map for a four terminal jack plugsuch as the jack plug shown in FIG. 1. For instance, as shown in the toprow, if the accessory device is a stereo headset with a microphone(MIC), terminals 1 and 2 of the plug may be used for left audio andright audio respectively and terminal 3 may be used for the microphoneconnection. The signals are referenced to terminal 4 (e.g., ground).

The terminals of a jack plug will be connected to different types ofcircuits based on the function of the accessory device. Because of thesedifferent circuits, the impedance measured at the terminals of the jackplug will have different values depending on the function of theaccessory device.

TABLE 1 Terminal Accessory Device Terminal 1 Terminal 2 3 Terminal 4Stereo Headset Left Audio Right Audio MIC GND with MIC Mono Headset MonoAudio Mono Audio MIC GND with MIC Standard 3.5 mm Left Audio Right AudioGND GND Headset A/V Cable Left Audio Right Audio Video GND

Table 2 shows an example of how impedances measured at the terminals canbe used to determine the type of accessory device plugged into the audiojack connector or the video jack connector. For instance, if impedancemeasured at terminals 1 or 2 is approximately 600 ohms (Ω) or less, theaccessory device includes a headset. If measured impedance determinesthat terminals land 2 are shorted together, the headset is amono-headset. Similarly, if the impedance measured at terminal 3 isabout 75Ω, the accessory device includes a television. If the impedanceat terminal 3 is approximately in the range of 1.1 kΩ-2.2 kΩ, theaccessory device includes a microphone. Multiple resistances may used toindicate multiple functions of the accessory device, such as headsetwith a microphone indicated by terminals 1 and/or 2, and terminal 3.

Measured impedance can also be used to determine the presence of thejack plug. For instance, a jack plug can be detected when the impedanceof any of the terminals has a value less than 500 kΩ. In anotherexample, a jack plug can be detected when the impedance of any of theterminals has a value less than 10 kΩ.

TABLE 2 Terminal No. Impedance Measured Device ID 1 and 2 600 Ω or lessHeadset 1 and 2 shorted Mono Headset 1 and 2 not shorted Stereo Headset1 and 2 Greater than 500 kΩ Open 3 GND Short - SEND/END press OrStandard Headset 3 75 Ω TV 3 1 kΩ to 2.2 kΩ Microphone 3 4 kΩ to 500 kΩButton Press Options 3 Greater than 500 kΩ Open

FIG. 2 shows a block diagram of portions of an example of a device 200to automatically detect the presence and type of an accessory devicethat is connected to it. The device 200 includes an audio or video jackconnector 205 that receives an audio or video jack plug of the separateaccessory device. The connector 205 includes an electrical contact forconnection to a conducting terminal of the plug.

In certain examples, the connector 205 includes two electrical contacts210A and 210B to receive a TS type connector plug. In certain examples,the connector 205 includes three electrical contacts 210A, 210B, and210C to receive a TRS type connector plug. In certain examples, theconnector 205 includes four electrical contacts 210A, 210B, 210C, and210D to receive a TRRS type connector plug.

The device also includes a detection circuit 215 in electricalcommunication with the connector 205. The detection circuit 215determines a resistance or impedance at one or more conducting terminalsof jack plug. The resistance determined is a resistive load of theseparate accessory device seen at the conducting terminal of the plug,and not merely the resistance of the conducting terminal.

FIG. 3 is a block diagram of portions of an example of a detectioncircuit 315. The resistor and capacitor R_(PIN) and C_(PIN) representthe impedance seen at a conducting terminal of a jack plug. Thedetection circuit 315 also includes a controllable current source 320and a comparator 325. The current source 320 outputs (e.g., sources orsinks) a current that is proportional to the digital value (idac[9:0])of an identification register. To determine the resistance of aconducting terminal, the detection circuit 315 changes (e.g., increases)the digital value of the register and provides the proportional currentto R_(PIN) to create a voltage V_(PIN) at an input of the comparator325. When V_(PIN) is approximately equal to V_(REF), a detect signal isgenerated by the detection circuit. The value of R_(PIN) is determinedfrom the known value of V_(REF) and the current value that correspondsto the digital value in the identification register.

The combined capacitance seen at the conducting terminal is theconduction terminal capacitance C_(PIN) and the internal capacitance ofthe connection C_(INT). Because of this capacitance, there is a timeconstant associated with the voltage V_(PIN) reaching its final value.The time for V_(PIN) to reach 50% of its final value is0.7R_(PIN)*(C_(PIN)+C_(INT)). The detection circuit 315 allows enoughtime for V_(PIN) to stabilize between measurements before changing thevalue of the identification register. In certain examples, the samedetection circuit 315 is used to determine the resistance of multipleconducting terminals, such as by using a switch circuit to switchdifferent terminals to the detection circuit input. In certain examples,a different detection circuit 315 is included for each conductingterminal.

Returning to FIG. 2, the device 200 also includes a processor 235communicatively coupled to the detection circuit. The communicativecoupling allows signals to be communicated to the processor 235 from thedetection circuit 215 even though there may be intervening circuitry. Insome examples, the processor 235 is a microprocessor. In some examples,the processor 235 is application specific integrated circuit (ASIC). Theprocessor 235 executes instructions in software and/or firmware toperform the function described herein. The software and/or firmware arecontained in modules. One or more functions may be performed by amodule.

The processor 235 identifies a function of the separate accessory deviceaccording to the determined resistance. In certain examples, if thedetection circuit 215 is the detection circuit 315 of FIG. 3, theprocessor 235 identifies a function of the separate device according tothe value of the identification register. The processor 235 thenconfigures operation of the device 200 according to the determinedfunction.

For instance, the connector 205 may include a first electrical contact210A for connecting to a first conducting terminal of the plug, and asecond electrical contact 210C for connecting to a second conductingterminal of the plug. Using the examples in Table 2, if the processordetermines that a measured resistance of one or more of the twoconducting terminals is 600Ω, then the accessory device includes aheadset and the processor 235 configures the device to provide audiosignals to the conducting terminals. If the processor 235 determinesthat the electrical contacts are shorted together (e.g., by connectingthe electrical contacts to the inputs of the detection circuit 215) thenthe accessory device is identified as a mono-headset. If the processor235 determines that the electrical contacts are not shorted together,then the accessory device is identified as a stereo-headset and theprocessor 235 provides stereo audio signals to the conducting terminals.

In some examples, the device 200 includes a media player. The processor235 is a baseband processor and the device 200 includes an audio codecmodule 240. The processor 235 configures the audio codec module 240according to the determined function of the separate accessory device.In certain examples, the processor 235 configures the audio codec module240 to provide mono or stereo audio signals to the conducting terminalsof the plug according to whether the determined function is mono audioor stereo audio.

The device 200 is not limited to only providing audio information. Insome examples, the processor 235 may determine that the accessory deviceincludes a microphone (e.g., by measuring a resistance in the range of 1kΩ to 2.2 kΩ at a third conducting terminal in the example of Table 2).The processor 235 configures the audio codec module 240 to receive audiosignals from the conducting terminals of the plug according to themeasured resistance.

The functions detected by the device 200 are not limited to audiofunctions. The accessory device may include a video display or monitor.In some examples, the device 200 includes a video processor 245. Theprocessor 235 may determine that the accessory device includes videocapability (e.g., by measuring a resistance of approximately 75Ω at athird conducting terminal in the example of Table 2). The processor 235configures the video processor 245 to provide video information to aconducting terminal of the plug.

FIG. 4 is a flow diagram of an example of a method 400 for automaticallydetecting the presence of an accessory device when it is connected to ahost device. At block 405, an audio or video jack plug of a first deviceis detected when inserted into an audio or video jack connector of asecond device. In this way, the second device automatically detects thepresence of the first device. In some examples, this may includedetecting that the connector of the second device is no longer seeing anopen circuit at its electrical contact or contacts. In certain examples,this occurs when current in the detection circuit begins flowing due topresence of a conducting terminal and creates a voltage V_(PIN) lessthan a threshold voltage (e.g., V_(REF)).

At block 410, a resistance at least one conducting terminal of the plugis determined using the second device. The resistance includes aresistive load of the first device measurable at the conducting terminalof the plug. At block 415, a function performable by the first device isidentified by the second device according to the resistance at the atleast one conducting terminal. At block 420, the second deviceautomatically configures itself according to the identified functionperformable by the first device.

Returning to FIG. 2, according to some examples, the device 200 includescontrol logic circuit 250 communicatively coupled to the processor 235.The processor 235 uses the control logic circuit 250 to configure thedevice 200 such as by changing the state of switches in the device 200.In some examples, the control logic circuit 250 communicates informationwith the processor 235 using an inter-integrated circuit protocol (I²C).The device 200 includes an I²C slave module 255 for communicating withthe processor 235.

FIG. 5 is a flow diagram of another example of a method 500 forautomatically detecting the presence of an accessory device when it isconnected to a host device. At block 505, the device 200 of FIG. 2detects from measured impedance that a user has plugged an audio orvideo jack plug of an accessory device into the connector of the device200.

At block 510, the resistance that identifies a function of the accessorydevice is determined. In some examples, the control logic circuit 250changes the digital value of an identification to change the measuringcurrent used by the detection circuit 215. When the detect signal isreceived from the detection circuit 215, the value stored in theidentification register of the control logic circuit 250 indicates thefunction.

At block 515, the control logic circuit 250 generates an interrupt tothe processor when the resistance has been determined by the detectioncircuit 215. The interrupt may be sent using the I²C protocol via theI²C slave module 255. At block 520, the processor 235 reads a value inthe identification register. In certain examples, the processor 235reads the identification register from the I²C slave module 255.

At block 525, the processor 235 determines (e.g., reads) the function ofthe accessory device using the value in the identification register. Forexample, the processor 235 may determine that the accessory deviceincludes a headset, a stereo headset, a microphone, or a video display.The processor 235 then configures the device 200 according to theidentified accessory device function. For instance, if the processor 235determines that the accessory device is a headset, the processor 235configures the control logic circuit 250 to switch audio information tothe conducting terminals such as by switch multiplexer 260 for example.If the processor 235 determines that the accessory device displaysvideo, the processor 235 configures the control logic circuit 250 toswitch video information to the conducting terminals, such as by switch265 for example. If the processor 235 determines that the accessorydevice includes a microphone, the processor 235 configures the controllogic circuit 250 to route audio information from the conductingterminals to the audio codec module 240, such as by switch 265 forexample.

According to some examples, the accessory device may be able to changethe resistance seen at one or more of the conducting terminals. Forinstance, the accessory device may include a switch to change theresistance at a conducting terminal of the jack plug when the switch isactivated by a user, such as by a button press for example. In someexamples, the resistance at the conducting terminal only changes whilethe user activates the switch (e.g., depresses the button).

In some examples, the detection circuit 215 first determines theresistance seen at a conducting terminal of the jack plug and thendetects the change in the determined resistance. As a result ofdetecting the change, a processor interrupt is generated by the controllogic circuit 250. In certain examples, the processor receives a valueindicative of the determined resistance in relation to the interrupt,such as from an identification register for example. The processor 235changes an operation of the device 200 in response to the detectedchange in the resistance. In certain examples, the processor 235initiates an operation identified according to the received value.

As an illustrative example, assume that, an initial resistancedetermined by the detection circuit 215 identifies an accessory deviceas including a headset. The resistance then changes from this initialresistance and the detection circuit 215 provides a value of theresistance to the processor 235. Based on the resistance value, theprocessor 235 then initiates an operation of the device 200 based on thevalue, such as stop, play, rewind, or fast forward. A non-exhaustivelist of possible examples of resistances for such operations include 4kΩ for stop, 5.62 kΩ for play, 7.87 kΩ for rewind, and 11 kΩ for fastforward. Other operations may include pause, skip, back, and volume upor down. In another example, the accessory device includes a videodisplay or monitor and the operation includes menu operations, such asselect, skip, play, fast forward and the like.

Different resistance values may be switched on to one or more conductingterminals to identify different operations for the same accessorydevice. In some examples, multiple keys of a headset with a keypad canbe monitored. This may be useful for controlling a media player of thehost device. In certain examples, the resistance change is only evidentwhile the user depresses a button and returns to an original resistancewhen the button is no longer pressed. The device 200 may detect that aswitch is stuck by monitoring the amount of time the change inresistance is evident.

In some examples, the device 200 includes a sense circuit 270communicatively coupled to the control logic circuit 250 to detectpresence of the plug. The detection circuit 215 detects a change in theresistance at the conducting terminal while the sense circuit 270detects that the plug remains connected. The processor 235 theninitiates an operation of the apparatus according to the detected changein resistance.

FIG. 6 is a flow diagram of an example of a method 600 for automaticallydetecting the presence of an accessory device when it is connected to ahost device and for identifying requested device operations. At block605, the device 200 of FIG. 2 detects from measured impedance that auser has plugged an audio or video jack plug of an accessory device intothe connector of the device 200. The measured impedance is seen at aconducting terminal of the jack plug, and at block 610, the host deviceidentifies the type of accessory device by the impedance.

At block 615, the detection circuit 215 detects a change in resistanceof a conducting terminal of the jack plug. The change may be at the sameconducting terminal used to identify the device or the impedance changemay be seen at a different conducting terminal of the jack plug. Thechange may be due to the user pushing a button on the accessory deviceor from the user activating a switch on the cable or wire attached tothe jack plug.

At block 620, an interrupt is generated when the resistance value isdetermined. The interrupt may be sent to the processor 235 of the device200 using an I²C protocol. The processor 235 then reads the valuecorresponding to the resistance, such as by reading an identificationregister.

At block 625, the processor 235 identifies the operation correspondingto the resistance caused by the button press or switch activation. Theprocessor 235 then initiates the operation. When the operationcompletes, the device waits for the next resistance change that signalsthe next device operation. It can be seen that this impedance monitoringallows the host device to detect the type of accessory plugged in so thehost device can configure itself appropriately and allows the hostdevice to continue to check for changes in status of the accessorydevice.

Additional Notes

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which theinvention can be practiced. These embodiments are also referred toherein as “examples.” All publications, patents, and patent documentsreferred to in this document are incorporated by reference herein intheir entirety, as though individually incorporated by reference. In theevent of inconsistent usages between this document and those documentsso incorporated by reference, the usage in the incorporated reference(s)should be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Also, in the following claims, theterms “including” and “comprising” are open-ended, that is, a system,device, article, or process that includes elements in addition to thoselisted after such a term in a claim are still deemed to fall within thescope of that claim. Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to impose numerical requirements on their objects.

Method examples described herein can be machine or computer-implementedat least in part. Some examples can include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods can include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code can include computer readable instructions forperforming various methods. The code can form portions of computerprogram products. Further, the code can be tangibly stored on one ormore volatile or non-volatile computer-readable media during executionor at other times. These computer-readable media can include, but arenot limited to, hard disks, removable magnetic disks, removable opticaldisks (e.g., compact disks and digital video disks), magnetic cassettes,memory cards or sticks, random access memories (RAM's), read onlymemories (ROM's), and the like.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features may be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter maylie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separateembodiment. The scope of the invention should be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1. An apparatus comprising: an audio or video jack connector configuredto receive an audio or video jack plug of a separate device, wherein theconnector includes an electrical contact for connection to a pluralityof conducting terminals arranged in series along a length of the plug; adetection circuit in electrical communication with the connector,wherein the detection circuit is configured to: determine a value ofresistance at a conducting terminal, wherein the resistance isrepresentative of a resistive load of the separate device at theconducting terminal of the plug; and a processor communicatively coupledto the detection circuit, wherein the processor is configured to:identify a function of the separate device according to a firstdetermined resistance value; configure an operation of the apparatusaccording to the determined function; and initiate a second operation ofthe second device according to a detected change from the firstresistance value to a second resistance value, wherein the change isdetected while a connection to the connector is maintained and afteridentification of the function performable by the separate device usingthe first resistance value.
 2. The apparatus of claim 1, wherein theprocessor is configured to initiate at least one of a stop, play rewind,or fast forward operation according to the determined second resistancevalue.
 3. The apparatus of claim 1 including a control logic circuitcommunicatively coupled to the detection circuit and the processor,wherein the control logic circuit is configured to generate an interruptto the processor when the change in the determined resistance isdetected, and wherein the processor is configured to receive a valueindicative of the determined resistance in relation to the interrupt andto initiate an operation identified according to the received value. 4.The apparatus of claim 3, wherein the control logic circuit communicatesinformation with the processor using an inter-integrated circuitprotocol (I²C).
 5. The apparatus of claim 1, including a sense circuitcommunicatively coupled to the control logic circuit to detect presenceof the plug, wherein the detection circuit is configured to detect achange in the resistance at the conducting terminal while the sensecircuit detects that the plug remains connected, and wherein theprocessor is configured to initiate the second operation of theapparatus according to the detected change in resistance.
 6. Theapparatus of claim 1, wherein the connector includes a first electricalcontact for connecting to a first conducting terminal of the plug, and asecond electrical contact for connecting to a second conducting terminalof the plug, and wherein the processor is configured to identify afunction of the separate device from a resistance determined at thefirst and second conducting terminal.
 7. The apparatus of claim 6,wherein the processor is configured to identify that the separate deviceincludes a headset from a resistance determined at the first and secondconducting terminal.
 8. The apparatus of claim 6, wherein the connectorincludes a third electrical contact for connecting to a third conductingterminal of the plug, and wherein the processor is configured toidentify that the separate device includes one of a video monitor or amicrophone according to a resistance determined at the third conductingterminal.
 9. The apparatus of claim 1, wherein the processor includes anaudio codec module, and wherein the processor configures the audio codecmodule according to the determined function of the separate device. 10.A system comprising: a first device including an audio or video jackplug, wherein the plug includes a plurality of conducting terminalsarranged in series along a length of the plug; a second deviceincluding: an audio or video jack connector to receive the plug of thefirst device; a detection circuit in electrical communication with theconnector, wherein the detection circuit is configured to determine avalue of resistance at a conducting terminal, wherein the resistance isrepresentative of a resistive load of the first device measurable at theconducting terminal; a processor communicatively coupled to thedetection circuit, wherein the processor is configured to: determine afunction of the separate device according to determined first resistancevalue; configure an operation of the second device according to thedetermined function; and initiate a second operation of the seconddevice according to a detected change from the first resistance value toa second resistance value, wherein the change is detected while aconnection to the connector is maintained and after identification ofthe function performable by the separate device.
 11. The system of claim10, wherein the detection circuit is configured to detect a change inthe determined resistance from the first resistance value to a secondspecified resistance value, and wherein the processor is configured toinitiate at least one of a stop, play rewind, or fast forward operationby the second device according to the determined second specifiedresistance value.
 12. The system of claim 10, wherein the plug includesat least a first conducting terminal, a second conducting terminal, anda ground terminal, and wherein the processor is configured to identifythat the first device includes a headset according to a resistancedetermined at the first conducting terminal and the second conductingterminal.
 13. The system of claim 12, wherein the plug includes a thirdconducting terminal and a ground terminal, and wherein the processor isconfigured to identify that the first device includes one of amicrophone or a video display according to a resistance determined atthe third conducting terminal.
 14. A method comprising: detecting thatan audio or video jack plug of a first device is inserted into an audioor video jack connector of a second device, wherein the connector of thesecond device includes an electrical contact for connection to aplurality of conducting terminals arranged in series along a length ofthe plug; determining a first resistance value at least one conductingterminal of the plug using the second device, wherein the firstresistance value is representative of a resistive load of the firstdevice measurable at the conducting terminal; identifying, using thesecond device, a function performable by the first device according tothe first resistance value; configuring the second device according tothe identified function performable by the first device; detecting,after the detection of the plug and after identification of the functionperformable by the first device, a change from the first resistancevalue to a second resistance value while the connection to the connectoris maintained; and initiating an operation of the second deviceaccording to the second resistance value.
 15. The method of claim 14,wherein identifying a function performable by the first device accordingto the resistance of the at least one conducting terminal includesidentifying, by the second device, that the first device includes aheadset, and wherein initiating an operation in the second deviceincludes initiating at least one of a stop, play, fast forward, pause,or rewind operation in the second device.
 16. The method of claim 14,wherein determining a resistance of at least one conducting terminal ofthe plug includes determining a resistance of a plurality of conductingterminals of the plug, wherein identifying a function performable by thefirst device includes identifying a function performable by the firstdevice according to the resistance of a first conducting terminal; andwherein the method includes: detecting, using the second device, achange in a determined resistance of a second conducting terminal; andinitiating an operation in the second device in response to the detectedchange in resistance of the second conducting terminal.
 17. The methodof claim 14, wherein determining a resistance of at least one conductingterminal of the plug includes determining a resistive load of at least afirst conducting terminal of the plug and of a second conductingterminal of the plug with respect to a ground terminal of the plug. 18.The method of claim 17, wherein identifying a function performable bythe first device includes identifying, by the second device according tothe determined resistive loads, that the first device includes one of astereo-headset or a mono-headset.
 19. The method of claim 14, whereinidentifying a function performable by the first device according to theresistance of the conducting terminal includes identifying, by thesecond device, that the first device includes a video display.
 20. Thesystem of claim 10, wherein the connector includes an electrical contactfor connection to at least a conducting terminal at a tip of the plugand a conducting sleeve of the plug.